In some of conventional charging control apparatuses and charging control methods for a battery as a secondary battery, when brake is applied during travelling of a vehicle, the vehicle is braked by a mechanical brake and a motor generator linked with an engine is operated as an electric generator, serving as an electric brake, so that regenerative current flows in a DC/DC converter via a power conversion circuit, whereby regenerative power is stored into the battery and a capacitor. In this case, the battery charging power may be kept substantially at a constant value from the start of regeneration (for example, see Patent Document 1).
If the battery charging power is kept substantially at a constant value from the start of regeneration, the battery voltage does not vary as greatly as the capacitor voltage, and therefore it is considered that the buttery current becomes substantially constant. Such control is due to consideration of making the charging current for the battery equal to or smaller than a permissible value for the battery. Thus, while the charging current for the battery is kept substantially at a constant value from the start of regeneration, charging control is performed such that the charging current does not exceed its permissible upper limit value. This is generally called battery current constant control, which is a general charging control method.